DOUBTS ABOUT HIVE, help friends

1; if for example I have 1000 HP, I earn 2.94% apr and if I vote regularly what apr% do I earn approximately from the votes?

2.94% is default what you earn just by staking. You can increase it by using your stake to vote and it depends on how efficient you are at voting.

What if I voted for my own posts and comments? Is it legal or not?

There's no one stopping you from doing it. There's no legal issue here, it's enabled by code to do it. Whether it is right or wrong will depend on your values and who is judging you. Because there is a monetary consequence such as enriching yourself with self votes, the same function can still be done for others where you vote on their posts and still earn a cut. For self voters, they maximize this earning which becomes a greed motive. I equate the act as seeing a dog licking its own balls.

Where does the 20% APR from save HBD come from?

Printed and coded by the blockchain, HBD will stop printing if the value of HBD is greater than 10% of the total Hive marketcap if I recall it right. So if the value of Hive goes lower, people will get Hive instead of HBD.

Can you see somewhere the approximate monthly % APR % of the pools by commissions ? even if they're past

If you know how to query the nodes, you can check arcange or dalz's post about the financial stats on the blockchain.